third_party/WebKit/Source/platform/image-decoders/gif/GIFImageDecoder.cpp

/*
 * Copyright (C) 2006 Apple Computer, Inc.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY APPLE COMPUTER, INC. ``AS IS'' AND ANY
 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE COMPUTER, INC. OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
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 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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#include "platform/image-decoders/gif/GIFImageDecoder.h"

#include "platform/image-decoders/gif/GIFImageReader.h"
#include "wtf/NotFound.h"
#include "wtf/PtrUtil.h"
#include <limits>

namespace blink {

GIFImageDecoder::GIFImageDecoder(AlphaOption alphaOption,
                                 ColorSpaceOption colorOptions,
                                 size_t maxDecodedBytes)
    : ImageDecoder(alphaOption, colorOptions, maxDecodedBytes),
      m_repetitionCount(cAnimationLoopOnce) {}

GIFImageDecoder::~GIFImageDecoder() {}

void GIFImageDecoder::onSetData(SegmentReader* data) {
  if (m_reader)
    m_reader->setData(data);
}

int GIFImageDecoder::repetitionCount() const {
  // This value can arrive at any point in the image data stream.  Most GIFs
  // in the wild declare it near the beginning of the file, so it usually is
  // set by the time we've decoded the size, but (depending on the GIF and the
  // packets sent back by the webserver) not always.  If the reader hasn't
  // seen a loop count yet, it will return cLoopCountNotSeen, in which case we
  // should default to looping once (the initial value for
  // |m_repetitionCount|).
  //
  // There are some additional wrinkles here. First, ImageSource::clear()
  // may destroy the reader, making the result from the reader _less_
  // authoritative on future calls if the recreated reader hasn't seen the
  // loop count.  We don't need to special-case this because in this case the
  // new reader will once again return cLoopCountNotSeen, and we won't
  // overwrite the cached correct value.
  //
  // Second, a GIF might never set a loop count at all, in which case we
  // should continue to treat it as a "loop once" animation.  We don't need
  // special code here either, because in this case we'll never change
  // |m_repetitionCount| from its default value.
  //
  // Third, we use the same GIFImageReader for counting frames and we might
  // see the loop count and then encounter a decoding error which happens
  // later in the stream. It is also possible that no frames are in the
  // stream. In these cases we should just loop once.
  if (isAllDataReceived() && parseCompleted() && m_reader->imagesCount() == 1)
    m_repetitionCount = cAnimationNone;
  else if (failed() || (m_reader && (!m_reader->imagesCount())))
    m_repetitionCount = cAnimationLoopOnce;
  else if (m_reader && m_reader->loopCount() != cLoopCountNotSeen)
    m_repetitionCount = m_reader->loopCount();
  return m_repetitionCount;
}

bool GIFImageDecoder::frameIsCompleteAtIndex(size_t index) const {
  return m_reader && (index < m_reader->imagesCount()) &&
         m_reader->frameContext(index)->isComplete();
}

float GIFImageDecoder::frameDurationAtIndex(size_t index) const {
  return (m_reader && (index < m_reader->imagesCount()) &&
          m_reader->frameContext(index)->isHeaderDefined())
             ? m_reader->frameContext(index)->delayTime()
             : 0;
}

bool GIFImageDecoder::setFailed() {
  m_reader.reset();
  return ImageDecoder::setFailed();
}

bool GIFImageDecoder::haveDecodedRow(size_t frameIndex,
                                     GIFRow::const_iterator rowBegin,
                                     size_t width,
                                     size_t rowNumber,
                                     unsigned repeatCount,
                                     bool writeTransparentPixels) {
  const GIFFrameContext* frameContext = m_reader->frameContext(frameIndex);
  // The pixel data and coordinates supplied to us are relative to the frame's
  // origin within the entire image size, i.e.
  // (frameContext->xOffset, frameContext->yOffset). There is no guarantee
  // that width == (size().width() - frameContext->xOffset), so
  // we must ensure we don't run off the end of either the source data or the
  // row's X-coordinates.
  const int xBegin = frameContext->xOffset();
  const int yBegin = frameContext->yOffset() + rowNumber;
  const int xEnd = std::min(static_cast<int>(frameContext->xOffset() + width),
                            size().width());
  const int yEnd = std::min(
      static_cast<int>(frameContext->yOffset() + rowNumber + repeatCount),
      size().height());
  if (!width || (xBegin < 0) || (yBegin < 0) || (xEnd <= xBegin) ||
      (yEnd <= yBegin))
    return true;

  const GIFColorMap::Table& colorTable =
      frameContext->localColorMap().isDefined()
          ? frameContext->localColorMap().getTable()
          : m_reader->globalColorMap().getTable();

  if (colorTable.isEmpty())
    return true;

  GIFColorMap::Table::const_iterator colorTableIter = colorTable.begin();

  // Initialize the frame if necessary.
  ImageFrame& buffer = m_frameBufferCache[frameIndex];
  if ((buffer.getStatus() == ImageFrame::FrameEmpty) &&
      !initFrameBuffer(frameIndex))
    return false;

  const size_t transparentPixel = frameContext->transparentPixel();
  GIFRow::const_iterator rowEnd = rowBegin + (xEnd - xBegin);
  ImageFrame::PixelData* currentAddress = buffer.getAddr(xBegin, yBegin);

  // We may or may not need to write transparent pixels to the buffer.
  // If we're compositing against a previous image, it's wrong, and if
  // we're writing atop a cleared, fully transparent buffer, it's
  // unnecessary; but if we're decoding an interlaced gif and
  // displaying it "Haeberli"-style, we must write these for passes
  // beyond the first, or the initial passes will "show through" the
  // later ones.
  //
  // The loops below are almost identical. One writes a transparent pixel
  // and one doesn't based on the value of |writeTransparentPixels|.
  // The condition check is taken out of the loop to enhance performance.
  // This optimization reduces decoding time by about 15% for a 3MB image.
  if (writeTransparentPixels) {
    for (; rowBegin != rowEnd; ++rowBegin, ++currentAddress) {
      const size_t sourceValue = *rowBegin;
      if ((sourceValue != transparentPixel) &&
          (sourceValue < colorTable.size())) {
        *currentAddress = colorTableIter[sourceValue];
      } else {
        *currentAddress = 0;
        m_currentBufferSawAlpha = true;
      }
    }
  } else {
    for (; rowBegin != rowEnd; ++rowBegin, ++currentAddress) {
      const size_t sourceValue = *rowBegin;
      if ((sourceValue != transparentPixel) &&
          (sourceValue < colorTable.size()))
        *currentAddress = colorTableIter[sourceValue];
      else
        m_currentBufferSawAlpha = true;
    }
  }

  // Tell the frame to copy the row data if need be.
  if (repeatCount > 1)
    buffer.copyRowNTimes(xBegin, xEnd, yBegin, yEnd);

  buffer.setPixelsChanged(true);
  return true;
}

bool GIFImageDecoder::parseCompleted() const {
  return m_reader && m_reader->parseCompleted();
}

bool GIFImageDecoder::frameComplete(size_t frameIndex) {
  // Initialize the frame if necessary.  Some GIFs insert do-nothing frames,
  // in which case we never reach haveDecodedRow() before getting here.
  ImageFrame& buffer = m_frameBufferCache[frameIndex];
  if ((buffer.getStatus() == ImageFrame::FrameEmpty) &&
      !initFrameBuffer(frameIndex))
    return false;  // initFrameBuffer() has already called setFailed().

  buffer.setStatus(ImageFrame::FrameComplete);

  if (!m_currentBufferSawAlpha) {
    // The whole frame was non-transparent, so it's possible that the entire
    // resulting buffer was non-transparent, and we can setHasAlpha(false).
    if (buffer.originalFrameRect().contains(IntRect(IntPoint(), size()))) {
      buffer.setHasAlpha(false);
      buffer.setRequiredPreviousFrameIndex(kNotFound);
    } else if (buffer.requiredPreviousFrameIndex() != kNotFound) {
      // Tricky case.  This frame does not have alpha only if everywhere
      // outside its rect doesn't have alpha.  To know whether this is
      // true, we check the start state of the frame -- if it doesn't have
      // alpha, we're safe.
      const ImageFrame* prevBuffer =
          &m_frameBufferCache[buffer.requiredPreviousFrameIndex()];
      ASSERT(prevBuffer->getDisposalMethod() !=
             ImageFrame::DisposeOverwritePrevious);

      // Now, if we're at a DisposeNotSpecified or DisposeKeep frame, then
      // we can say we have no alpha if that frame had no alpha.  But
      // since in initFrameBuffer() we already copied that frame's alpha
      // state into the current frame's, we need do nothing at all here.
      //
      // The only remaining case is a DisposeOverwriteBgcolor frame.  If
      // it had no alpha, and its rect is contained in the current frame's
      // rect, we know the current frame has no alpha.
      if ((prevBuffer->getDisposalMethod() ==
           ImageFrame::DisposeOverwriteBgcolor) &&
          !prevBuffer->hasAlpha() &&
          buffer.originalFrameRect().contains(prevBuffer->originalFrameRect()))
        buffer.setHasAlpha(false);
    }
  }

  return true;
}

size_t GIFImageDecoder::clearCacheExceptFrame(size_t clearExceptFrame) {
  // We expect that after this call, we'll be asked to decode frames after
  // this one.  So we want to avoid clearing frames such that those requests
  // would force re-decoding from the beginning of the image.
  //
  // When |clearExceptFrame| is e.g. DisposeKeep, simply not clearing that
  // frame is sufficient, as the next frame will be based on it, and in
  // general future frames can't be based on anything previous.
  //
  // However, if this frame is DisposeOverwritePrevious, then subsequent
  // frames will depend on this frame's required previous frame.  In this
  // case, we need to preserve both this frame and that one.
  size_t clearExceptFrame2 = kNotFound;
  if (clearExceptFrame < m_frameBufferCache.size()) {
    const ImageFrame& frame = m_frameBufferCache[clearExceptFrame];
    if ((frame.getStatus() != ImageFrame::FrameEmpty) &&
        (frame.getDisposalMethod() == ImageFrame::DisposeOverwritePrevious)) {
      clearExceptFrame2 = clearExceptFrame;
      clearExceptFrame = frame.requiredPreviousFrameIndex();
    }
  }

  // Now |clearExceptFrame| indicates the frame that future frames will
  // depend on.  But if decoding is skipping forward past intermediate frames,
  // this frame may be FrameEmpty.  So we need to keep traversing back through
  // the required previous frames until we find the nearest non-empty
  // ancestor.  Preserving that will minimize the amount of future decoding
  // needed.
  while ((clearExceptFrame < m_frameBufferCache.size()) &&
         (m_frameBufferCache[clearExceptFrame].getStatus() ==
          ImageFrame::FrameEmpty))
    clearExceptFrame =
        m_frameBufferCache[clearExceptFrame].requiredPreviousFrameIndex();
  return clearCacheExceptTwoFrames(clearExceptFrame, clearExceptFrame2);
}

size_t GIFImageDecoder::clearCacheExceptTwoFrames(size_t clearExceptFrame1,
                                                  size_t clearExceptFrame2) {
  size_t frameBytesCleared = 0;
  for (size_t i = 0; i < m_frameBufferCache.size(); ++i) {
    if (m_frameBufferCache[i].getStatus() != ImageFrame::FrameEmpty &&
        i != clearExceptFrame1 && i != clearExceptFrame2) {
      frameBytesCleared += frameBytesAtIndex(i);
      clearFrameBuffer(i);
    }
  }
  return frameBytesCleared;
}

void GIFImageDecoder::clearFrameBuffer(size_t frameIndex) {
  if (m_reader &&
      m_frameBufferCache[frameIndex].getStatus() == ImageFrame::FramePartial) {
    // Reset the state of the partial frame in the reader so that the frame
    // can be decoded again when requested.
    m_reader->clearDecodeState(frameIndex);
  }
  ImageDecoder::clearFrameBuffer(frameIndex);
}

size_t GIFImageDecoder::decodeFrameCount() {
  parse(GIFFrameCountQuery);
  // If decoding fails, |m_reader| will have been destroyed.  Instead of
  // returning 0 in this case, return the existing number of frames.  This way
  // if we get halfway through the image before decoding fails, we won't
  // suddenly start reporting that the image has zero frames.
  return failed() ? m_frameBufferCache.size() : m_reader->imagesCount();
}

void GIFImageDecoder::initializeNewFrame(size_t index) {
  ImageFrame* buffer = &m_frameBufferCache[index];
  const GIFFrameContext* frameContext = m_reader->frameContext(index);
  buffer->setOriginalFrameRect(
      intersection(frameContext->frameRect(), IntRect(IntPoint(), size())));
  buffer->setDuration(frameContext->delayTime());
  buffer->setDisposalMethod(frameContext->getDisposalMethod());
  buffer->setRequiredPreviousFrameIndex(
      findRequiredPreviousFrame(index, false));
}

void GIFImageDecoder::decode(size_t index) {
  parse(GIFFrameCountQuery);

  if (failed())
    return;

  updateAggressivePurging(index);

  Vector<size_t> framesToDecode;
  size_t frameToDecode = index;
  do {
    framesToDecode.append(frameToDecode);
    frameToDecode =
        m_frameBufferCache[frameToDecode].requiredPreviousFrameIndex();
  } while (frameToDecode != kNotFound &&
           m_frameBufferCache[frameToDecode].getStatus() !=
               ImageFrame::FrameComplete);

  for (auto i = framesToDecode.rbegin(); i != framesToDecode.rend(); ++i) {
    if (!m_reader->decode(*i)) {
      setFailed();
      return;
    }

    // We need more data to continue decoding.
    if (m_frameBufferCache[*i].getStatus() != ImageFrame::FrameComplete)
      break;

    if (m_purgeAggressively)
      clearCacheExceptFrame(*i);
  }

  // It is also a fatal error if all data is received and we have decoded all
  // frames available but the file is truncated.
  if (index >= m_frameBufferCache.size() - 1 && isAllDataReceived() &&
      m_reader && !m_reader->parseCompleted())
    setFailed();
}

void GIFImageDecoder::parse(GIFParseQuery query) {
  if (failed())
    return;

  if (!m_reader) {
    m_reader = wrapUnique(new GIFImageReader(this));
    m_reader->setData(m_data);
  }

  if (!m_reader->parse(query))
    setFailed();
}

bool GIFImageDecoder::initFrameBuffer(size_t frameIndex) {
  // Initialize the frame rect in our buffer.
  ImageFrame* const buffer = &m_frameBufferCache[frameIndex];

  size_t requiredPreviousFrameIndex = buffer->requiredPreviousFrameIndex();
  if (requiredPreviousFrameIndex == kNotFound) {
    // This frame doesn't rely on any previous data.
    if (!buffer->setSizeAndColorSpace(size().width(), size().height(),
                                      colorSpace())) {
      return setFailed();
    }
  } else {
    ImageFrame* prevBuffer = &m_frameBufferCache[requiredPreviousFrameIndex];
    ASSERT(prevBuffer->getStatus() == ImageFrame::FrameComplete);

    // We try to reuse |prevBuffer| as starting state to avoid copying.
    // For DisposeOverwritePrevious, the next frame will also use
    // |prevBuffer| as its starting state, so we can't take over its image
    // data using takeBitmapDataIfWritable.  Copy the data instead.
    if ((buffer->getDisposalMethod() == ImageFrame::DisposeOverwritePrevious ||
         !buffer->takeBitmapDataIfWritable(prevBuffer)) &&
        !buffer->copyBitmapData(*prevBuffer))
      return setFailed();

    if (prevBuffer->getDisposalMethod() ==
        ImageFrame::DisposeOverwriteBgcolor) {
      // We want to clear the previous frame to transparent, without
      // affecting pixels in the image outside of the frame.
      const IntRect& prevRect = prevBuffer->originalFrameRect();
      ASSERT(!prevRect.contains(IntRect(IntPoint(), size())));
      buffer->zeroFillFrameRect(prevRect);
    }
  }

  // Update our status to be partially complete.
  buffer->setStatus(ImageFrame::FramePartial);

  // Reset the alpha pixel tracker for this frame.
  m_currentBufferSawAlpha = false;
  return true;
}
}  // namespace blink